noise improvements

tests/test_noise.py

@@ -55,6 +55,20 @@ def test_time_and_back():
     assert new_noise.psd == pytest.approx(noise.psd)
 
 
+def test_nyquist():
+    """
+    generating a time series and tranforming it back yields the same spectrum.
+    Using segements, the nyquist frequency at least is the same
+    """
+    signal = np.cos(np.arange(1024) * np.pi)
+
+    n1 = sc.noise.NoiseMeasurement.from_time_series(signal, 1, None, 1)
+    n3 = sc.noise.NoiseMeasurement.from_time_series(signal, 1, None, 3)
+    n15 = sc.noise.NoiseMeasurement.from_time_series(signal, 1, None, 15)
+
+    assert n1.psd[-1] == n3.psd[-1] == n15.psd[-1]
+
+
 def test_sampling():
     f = np.geomspace(10, 2e6, 138)
     spec = 1 / (f + 1)